Johnson has also admitted to smoking marijuana as recently as 2008 to alleviate pain stemming from a paragliding accident in Hawaii.
The former governor is not the only Republican candidate to oppose the drug war.
Ron Paul has called for the end of the War on Drugs, calling the program overly expensive and burdensome. Paul, like Johnson a libertarian, has also said that Americans should have the freedom to choose if they want to take drugs.
"I hate the war on drugs a lot more than I fear drugs themselves, and I hate drugs," Paul said on the Daily Show with Jon Stewart.
Johnson has been in the low single digits of most national polls of the Republican field, but said that his position on marijuana legalization was not what was holding him back with socially conservative voters. Instead, Johnson attributes the shift to polarization under a two-party system that makes it tough for non-establishment candidates to break through.
Johnson appeared at the last Republican debate in Florida, although it has not yet been determined if he will qualify for the next debate at Dartmouth College in New Hampshire.